Rational Design of Environmental Benign Organic-Inorganic Hybrid as

Subscriber access provided by IDAHO STATE UNIV

C: Energy Conversion and Storage; Energy and Charge Transport

Rational Design of Environmental Benign Organic-Inorganic Hybrid as a Prospective Cathode for Stable High Voltage Sodium Ion Batteries Karthikeyan Kaliyappan, Zhengyu Bai, and Zhongwei Chen J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b01477 • Publication Date (Web): 22 Apr 2019 Downloaded from http://pubs.acs.org on April 22, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Rational Design Of Environmental Benign Organic-Inorganic Hybrid As A Prospective Cathode For Stable High Voltage Sodium Ion Batteries Karthikeyan Kaliyappan1,2, Zhengyu Bai1,*, and Zhongwei Chen2,* 1

School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China

2

Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada Abstract

An eco-friendly cobalt-free O3-Na[Ni1/3Mn1/3Fe1/3]O2 (NNMF), embedded on conductive polyaniline (PANI) backbones is synthesized as a hybrid cathode by a facile chemical polymerization technique. As a cathode for rechargeable sodium ion batteries (RSIB), the NNMF with 0.3 M of PANI (NNMF-PANI3) hybrid electrode displays enhanced energy density of 567 Wh kg-1 at a high operating voltage of 2-4.5 V along with excellent cyclic performance. In addition, the NNMF-PANI3 hybrid electrode exhibits ~ 75 % capacity retention after 750 cycles at 2 A g-1 current density within 2-4.5 V. Conversely, the pristine NNMF electrode without PANI fails to demonstrate adequate electrochemical performance even at a low cut-of voltage range (2-4.2 V). The superior electrochemical performance of the hybrid electrode is attributed to effective Na-ion transportation within the hybrid structure, in which PANI keeps the NNMF particles interconnected uniformly and offers better conductive contact between the electrolyte and the active species. Moreover, the presence of porous PANI networks allow more electrolyte penetration within its structure and eliminates the inherent mechanical stress during the 1 ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 41

electrochemical Na-ion intercalation/deintercalation at high currents. The results obtained in the present investigation reveals that organic-inorganic hybrids could be realized as promising ecofriendly high-performance cathode materials for RSIB applications. *Corresponding

author;

Email:

Dr.

Chen

([email protected]),

Dr.

Bai

([email protected]) Introduction Lithium ion batteries (LIBs) are currently being used as power sources for automotive applications such as electric vehicles (EVs) and hybrid electric vehicles (HEVs) due to their high working voltage, long term stability and large energy densities. 1 However, the high cost, limited lithium sources and toxic nature of LIBs have driven researchers to search for alternative power sources for these applications. 2 Because of the abundance of sodium in the Earth’s crust, low cost and environmentally friendly behavior, rechargeable sodium ion batteries (RSIBs) could be considered as the best alternative for LIB. 3 Although the initial studies on RSIBs began in the early 1980s, sodium’s relatively high atomic weight, low working voltage and lower energy densities restricted the choice of host materials for such applications.

2, 4-5

However, since the

demand for large scale batteries has rapidly increased in recent times, a primary target should be focused on fabricating large scale batteries which are not harmful to the environment and use a chemical element that is not resource-limited. Considering these circumstances and the safetyrelated problems of LIB, the development of energy storage materials for RSIB is completely justified. After 2010, intensive studies were dedicated to finding suitable high-performance electrode materials for RSIB. 2-3, 6 Surprisingly, some of the sodium-based host cathodes showed 2 ACS Paragon Plus Environment

Page 3 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


unique electrochemical properties compared to their lithium analogues.

7 8

So far, numerous

compounds including olivines, NASICON structures, pyrophosphates and layered oxides have been reported as positive electrode materials for RSIB applications. 2-3, 6, 8-10 11-12 Among them, layered transition metal oxides (NaMO2, M = Ni, Mn, Co and Fe) are being explored extensively as high capacity electrode materials.13-14 Unlike its lithium counterparts, NaMO2 possesses different crystal structures based on the stacking of oxygen layers in which Na-ions are located either in octahedral (O3-type) or in prismatic (P2-type) sites between the layers of the transition metal octahedra MO6.5 4 Numerous sodium-based layered metal oxides have been found to show Na-ion storage behavior within various voltage ranges. 2-4, 6, 8, 15 16-18 19-20 21 22 Composed of a cubic close-packed oxygen array, O3-type layered α-NaFeO2 is one of the most attractive positive cathode materials in terms of both volumetric and gravimetric energy density as well as its abundant raw material availability.23, 5 α-NaFeO2 has displayed electrochemical activity with ~ 80 mAh g-1 capacity along with a voltage plateau at 3.3 V according to the Fe3+/Fe4+ redox couple. 23-25

However, the Na/NaFeO2 cell experienced severe capacity fading when the operating voltage

was increased above 3.5 V. This capacity decay mainly resulted from the irreversible phase transformation attributed to the iron migration during the sodium removal step, resulting in the loss of Na-ion conduction paths as confirmed by ex-situ X-ray diffraction studies. 24, 26 To minimize the irreversible phase transformation, attempts have been made to substitute nickel and manganese for iron in NaFeO2. The foreign metal doping in iron sites has significantly enhanced the energy density and stability of NaFeO2-based electrode materials.

27

Recently,

layered O3-NaFex(Ni1/2Mn1/2)1-xO2 (x = 0, 0.4, 0.6, and 1.0) was developed and its potential application in RSIB was investigated, displaying a discharge capacity of ~ 130 mAh g-1 at 0.1 C rate within 2-3.8 V along with poor rate performance.8 Yoshida et al have proposed NaFe0.5Co0.5O2 3 ACS Paragon Plus Environment


Page 4 of 41

as a high energy and power density positive electrode for RSIB, which delivered high capacity but still contained the toxic and expensive cobalt element, increasing the overall cost of the battery system. 28 Later, Kim et al proposed that Na[Ni1/3Fe1/3Mn1/3]O2 (NNMF) cathode materials can deliver a discharge capacity of ~ 125 mAh g-1 at 0.1 C rate between 2 and 4 V. 29 However, the rate performance of NNMF was not showed in their report, which is one of the pre-requisites to power EVs and HEVs. It is well known that replacement of Co by Fe in the layered matrix reduces the electronic conducting profile when compared to the parent Na(Mn1/3Ni1/3Co1/3)O2, which restricts its high rate performance.30 In addition, the use of the Fe3+/4+ couple in electrochemical energy storage reactions is very difficult.29 Therefore, conductive coatings or composites are necessary to achieve high-performance Na insertion electrodes. To alleviate the inherent non-conductive properties of NNMF compounds, the concept of designing a hybrid cathode with a conducting polymer matrix is being adopted to form inorganicorganic composites as high-performance cathode materials. Among the conducting polymers, polyaniline (PANI) typically has certain advantages, including higher chemical stability, higher electrical conductivity, better acid/base properties and more stable electrochemical behavior.31 Besides, the large surface area and the doping and de-doping effects of PANI with many metal ions make PANI as the suitable candidate to prepare organic-inorganic hybrid cathodes for energy storage applications.32 There are some reports available on polymer-based hybrid cathodes to enhance the conductive nature of lithium intercalation materials such as LiFePO4, LiNi0.8Co0.2O2 and Li(Mn1/3Ni1/3M1/3)O2 (M = Co and Fe) for LIB applications. 32-36

37

However, to the best of

our knowledge the electrochemical performances of such hybrids as cathode active materials in RSIBs has yet to be explored. Hence, we are reporting the use of a novel organic-inorganic hybrids (NNMF-PANI) as high-performance Na-ion insertion host materials for the first time. Compared 4 ACS Paragon Plus Environment

Page 5 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


to carbon coating, the PANI backbone is physically bound to the NNMF particles and thereby increases the overall surface area, offering more active reaction sites for electrochemical Na insertion/reinsertion reactions. The polymer network between the particles also enhances Na-ion movement to maximize electrolyte access at high current and cut-off voltages. The impact of different molar concentrations of PANI on the electrochemical performance of NNMF has also been investigated in this work and is explained in detail. Experimental section Synthesis of NNMF A mixed hydroxide route is used to synthesis NNMF particles in which Na2CO3, NaOH, Ni(NO3)2, Fe(NO3)2.9H2O, and Co(NO3)2 are used as starting materials. In a typical synthesis, stoichiometric amounts of Fe, Ni and Mn nitrates are dissolved separately in distilled water and then mixed together. An appropriate amount of aqueous NaOH is then added dropwise to the above mixture and stirred for 6 h to produce mixed hydroxide precipitates. Then the hydroxide precipitates are filtered and washed to remove residual excess NaOH and dried at 80 oC for 24 h. The NNMF powders are obtained by firing the precipitates with excess amount of Na2CO3 at 850 oC

for 12 h in air.

Preparation of NNMF-PANI hybrids The hybrid material is prepared thorough chemical polymerization process. Initially, aniline monomer (0.1 M) and 0.5 g of NNMF are dispersed in 0.1 M HCl solution and sonicated for 15 mins. Then, an appropriate amount of ammonium persulfate (APS) dissolved in 0.1 M HCl is added into the abovementioned solution to start the polymerization process. The reaction takes place under constant stirring for 2 h at room temperature. In this reaction, APS and HCl act as 5 ACS Paragon Plus Environment


Page 6 of 41

oxidative agent and dopant, respectively, with the dopant used to enhance the conductivity of the polymer matrix. Finally, the NNMF-PANI powders are filtered and washed with ethanol several times and dried at 80 oC under vacuum. It is also important to study the impact of different molar concentrations of polyaniline on the electrochemical stability of pristine NNMF electrode materials. Hence, hybrid composite with different aniline molar ratios (0.2 and 0.3 M) are also prepared in the same way as described above. The NNMF-PANI hybrid electrodes prepared with 0.1, 0.2 and 0.3 M of aniline are denoted as NNMF-PANI1, NNMF-PANI2 and NNMF-PANI3, respectively. The PANI content in the composites are measured using TGA analysis, which are about 3.9, 7.8 and 10.2 wt% for NNMF-PANI1, NNMF-PANI2 and NNMF-PANI3, respectively. Characterization The phase purities of the prepared materials are examined using X-ray diffraction (XRD) in a Miniflex 600 (Rigaku, Japan) diffractometer spectrometer with Kα radiation (λ = 1.5406 nm). The surface morphology of pristine and NNMF-PANI hybrids are recorded in a field emission scanning electron microscope (FE-SEM, LEO Zeiss 1550, Switzerland) coupled with Energydispersive X-ray spectroscopy (EDS). The amount of PANI in NNMF-PANI is calculated by thermogravimetric analysis (TGA) between 0 and 400 oC at a rate of 5 oC min-1 in a thermal analyzer system (TGA, TA instrument Q500). Brunauer-Emmett-Teller (BET) surface area analysis was performed using an ASAP 2020 surface analyzer (Micromeritics, USA). Fourier transform infrared (FT-IR) spectroscopy is conducted on an IRPresitge-21 spectrometer (Japan). CR2032 type coin cell configuration is used to measure the electrochemical performance of the prepared electrodes in 1 M NaClO4-ethylene carbonate/diethyl carbonate (EC/DEC, 1:1 vol.) electrolyte. The coin cells were fabricated by sandwiching a slurry cathode, a polypropylene 6 ACS Paragon Plus Environment

Page 7 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


separator (Celgard 2400) and a Na foil counter electrode. The slurry cathodes are prepared by mixing of 70 % active materials (NNMF or PANI or NNMF-PANI composites), 20 % Ketjen black and 10 % of Teflonized acetylene black binder and pressed on stainless steel mesh current collector. The charge-discharge (C-D) studies are conducted at different potential ranges and different current densities (1 C = 240 mA g-1) using a Land Battery Test System. The cyclic voltammetry (CV) and electrochemical impedance (EIS) studies are performed using an electrochemical analyzer (VPS-300, Bio-Logic, France). Results and discussion The Rietveld refinement analysis of NNMF and NNMF-PANI hybrid cathodes are presented in fig. 1. The refinement fittings are done based on the assumption of occupancy of alkali, metal and oxygen ions in 3a, 3b and 6c sites, respectively. The fitted structure based on αNaFeO2 type with R3m space group was shown as inset in fig. 1a. The metal and sodium ions occupy the alternate layers in closed cubic framework of oxygen.33 It is clear from fig. 1a-1d that the difference between the original and fitted patterns is very small, which is further verified by the low difference between Rp % and Rwp % (listed in table 1). The XRD pattern of the NNMFPANI hybrids in fig. 1 (also presented in fig. S1) does not display peaks related to the PANI nanofibers, indicating the amount of PANI in NNMF-PANI hybrids is too low to be detected by XRD signals.29, 34-35 In addition, all patterns have intense and sharp XRD peaks, which reveals the highly crystalline nature of the prepared samples. The lattice parameters a and c, c/a ratios, and I(003)/I(104) ratios of pristine and hybrid cathodes are summarized in table 1. The hexagonal unit parameters of both pristine and hybrid materials (ah, ch and c/a) are almost same, revealing that the crystal structure of NNMF is not affected after the chemical polymerization process. The c/a ratio is a critical indicator of the hexagonal nature of any layered materials, and when c/a is greater than 7 ACS Paragon Plus Environment


Page 8 of 41

4.9, the material owns typical layered characteristics. As seen from table 1, the c/a ratios of all samples are more than 4.9, confirming their well-defined layered properties. The calculated mass percentage of Na, Ni, Mn and Fe using ICP-EOS analysis is found to be 0.952, 0.321, 0.319 and 0.315, respectively, which closely matches the expected ratio of NNMF. The surface morphology of the prepared samples is illustrated in fig. 2. As seen from the SEM and TEM image in fig. S2 and 2a, respectively, NNMF prepared using mixed hydroxide method showed rapid particle coarsening with the primary particle size ranging from 200 to 400 nm, The TEM image of PANI in fig. 2b presents the formation of abundant nanofibers having about 50 nm diameter and about 500 nm length during the chemical polymerization of the aniline monomer. PANI fibers also typically have uniform size and distribution along with agglomerated surface morphology because of the overlapping of nanofibers.32, 33 It can also be seen from the TEM image of PANI in fig. 2b that the nanofibers indeed have uniform size and distribution. Meanwhile, the PANI nanofibers display a BET surface area of ~ 63 m2 g-1. The pore size distribution of PANI fibers calculated using BJH analysis is illustrated in fig. S3. The BJH curves of PANI fibers confirms the presence of porous structures on the surface, which is a desirable feature for effective ion transportation during the C-D process.33, 36, 38 On the other hand, the TEM image of NNMF-PANI hybrids in fig. 2c-2e clearly shows that the exitance of a porous PANI matrix between the NNMF particles with different levels of PANI distribution. It is evident from the TEM images that the NNMF-PANI3 (fig 2e) composite has more uniform PANI backbone distribution compared to pristine and NNMF-PANI1 (fig 2c) and NNMF-PANI2 (fig 2d) composites. The unprotected NNMF particle surfaces in NNMF-PANI1 and NNMF-PANI2 allows the acidic electrolyte to attack the particles and results in the dissolution of the electroactive materials into the electrolyte. This causes severe capacity decay upon the cycling process. It is 8 ACS Paragon Plus Environment

Page 9 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


worth mentioning here that the linear distribution of the PANI matrix between the NNMF particles in NNMF-PANI3 hybrid ensures higher electrode/electrolyte interfacial conduct, thus facilitating Na-ion diffusion under high current operations and alleviates the intrinsic poor rate capability of other Fe based electrodes.34,35,39 The flexible structure significantly enhances the Na-ion movement further and reduces the mechanical stresses inherent during high current cycling,33,34 and hence the volume changes/cracks on electrodes could be effectively eliminated. 34,34,35 Fig. 2f displays a simple representation of ionic/electronic transfer though the conductive porous PANI network. This network also allows the electrode to store more electrolyte within its structure, providing more reactive sites for energy storage. The atomic level distribution of all elements is also examined using EDS analysis. The EDS elemental maps of NNMF and NNMF-PANI1, NNMF-PANI2 and NNMF-PANI3 hybrids are presented in fig. S4-S7, respectively. It is revealed from EDX mapping that the atomic level mixing of Fe, Co, Ni, and Na ions is uniformly distributed with similar intensities in both pristine and hybrid materials. The C and N mapping of NNMFPANI3 in fig. S6 further confirms the uniform distribution of porous PANI nanofibers between the NNMF particles, which acts as backbone to interconnect the NNMF particles. Initially, the Na-ion storage behavior of the NNMF electrode is examined at a lower potential window of 2-4.2 V at low current densities, as iron-based materials have relatively poor conductive properties.29-33 Fig. 3a and 3b presents the C-D and cyclic performance of the pristine NNMF electrode, respectively, measured at the low current of 0.02 A g-1 within a potential range of 2-4.2 V. The NNMF delivered a discharge capacity of about 132 mAh g-1 at 0.02 A g-1 current density, which is slightly higher than the previous report.29 The NNMF electrode shows a smooth and monotonous C-D curve, which is the typical behavior of layered materials and is also correlated well with the C-D curve of Na1.0Li0.2(Ni0.25Mn0.75)Oδ, confirming the single phase 9 ACS Paragon Plus Environment


Page 10 of 41

reaction. 29, 39 In addition, the oxidation and reduction plateau of Ni2+/4+ could be seen around 4.1 and 3.6 V during the charge and discharge process, respectively. It is clear that the capacity from NNMF electrode is mainly realized from the Ni2+/4+ redox couple while the Mn and Fe ions in the NNMF component act as stabilizing agents to retain the crystal structure during the Ni4+/2+ redox couple.40 34 It is clear from fig. 3b that the NNMF electrode exhibits stable cycling performance up to 50 cycles at lower current density. However, the rate performance of NNMF is not good enough for practical applications. The NNMF electrode delivers discharge capacities of ~ 62 and 30 mAh g-1 at 0.1 and 0.2 A g-1 current densities, respectively. As previously mentioned, it is well known that the rate performance of any iron-based electrode material is mainly influenced by its poor conductive nature, 34, 36 and hence a strong conductive coating/network is necessary to realize its full capability.34,

36

In this regard, a porous PANI conductive network is introduced between

NNMF particles to improve the inherent conductivity.36 Before testing the electrochemical performance of NNMF-PANI hybrid electrodes, the Na-ion insertion/reinsertion performance of PANI nano fibers was tested at 0.2 A g-1 current between 2 and 4.2 V in 1 M NaClO4 electrolyte. Fig 3c presented the C-D of the Na+/PANI half-cell at 0.2 A g-1 current density, which revealed that PANI is electrochemically active and can accommodate Na-ions during electrochemical reaction. The Na+/PANI cell delivered ~ 54 mAh g-1 capacity and maintained good capacity retention, as shown in fig. 3d. The influence of PANI concentration on the conductive profile of the NNMF electrodes has been studied by EIS spectra with the results are in fig 4a. The Nyquist plots of pristine NNMF and NNMF-PANI hybrids with different PANI concentrations show two main regions: a semicircle in the high-frequency region and an inclined line in the low-frequency region.33 The 10 ACS Paragon Plus Environment

Page 11 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


former is derived from the charge-transfer process across the electrode/electrolyte interface (charge-transfer resistance, Rct) and the latter is associated with the diffusion-controlled process of Na-ions (Warburg resistance). 35 The EIS spectra are fitted based on the equivalent circuit shown in the insert in fig. 4a. As seen from fig. 4a, the NNMF-PANI3 electrode displayed Rct of ~ 118.1 Ω, which is much lower than the NNMF (204.6 Ω), NNMF-PANI1 (180.3 Ω) and NNMF-PANI2 (148.8 Ω) electrodes. The lower Rct value of NNMF-PANI3 hybrid electrode is ascribed to the improvement in electronic conducting profiles supported by the more uniform distribution of polymer backbone and good adherence properties of the PANI on the current collector.31,33 This leads to better electrochemical Na-ion properties even at high applied currents and wide potential ranges. The sodium ion diffusion co-efficient (DNa) of NNMF and NNMF-PANI were calculated based on the following equation D = 1/2[R2T2/ S2n4F4C2σ2] where n is the number of electrons involved in the electrochemical reaction (n = 1), S is the electrode surface area (1 cm2), R is the universal gas constant (8.314 J mol-1 K-1), T is the absolute temperature (298.15 K), F is the Faraday constant (96,485 C mol-1), and C is the molar concentration of Na ions in the electrolyte. σ represents the Warburg factor that is calculated from the slope of the Warburg line in the EIS spectra. Based on equation (1), the calculated DNa for NNMF-PANI1 and NNMF was 4.72 × 10-13, 3.47 × 10-13, 3.23 × 10-13 and 2.31 × 10-13 cm2 s-1, respectively. It is clear that the sodium ion diffusion rate within the NNMF-PANI3 hybrid is higher that the bare NNMF electrode, resulting in lower polarization.33 It is important to achieve high capacity and stability at high voltage cut-off operation to adopt any electrode materials for large scale applications. Hence, the organic-inorganic hybrid 11 ACS Paragon Plus Environment


Page 12 of 41

cathodes are tested at high voltage window of 2-4.5 V. The electrochemical C-D profile of the NNMF electrode at 0.1 A g-1 current density within 2-4.5 V is displayed in fig. 4b. The electrode delivered around 110 mAh g-1 capacity with severe capacity decay, as its cyclic performance (shown as insert in fig. 4b) clearly shows only 27 % of capacity retention after 100 cycles. The deep capacity decay with high cut-off voltage is probably due to its low conductive property and the dissolution of active materials into the electrolyte.32 Although the pristine NNMF electrode exhibits very stable C-D behaviour within 2-4.2 V as shown in fig 3b, it failed to maintain the stability at high cut-off voltage even at low current density (insert in fig 4b). The electrochemical C-D and cyclic behaviour of NNMF-PANI1, NNMF-PANI2 and NNMF-PANI3 are presented in fig 4c and 4d, respectively. The NNMF-PANI1, NNMF-PANI2 and NNMF-PANI3 electrodes show discharge capacities of 113, 113 and 115 mAh g-1, respectively at 0.75 A g-1 current density within 2-4.5 V. Despite delivering almost the same discharge capacity values in the first cycle, continuous capacity fading is observed for NNMF-PANI1 and NNMF-PANI2, whereas the cell constructed with NNMF-PANI3 has very stable electrochemical stability as presented in fig 4d. Moreover, the NNMF-PANI1, NNMF-PANI2 and NNMF-PANI3 electrodes exhibit initial coulombic efficiencies of about 73, 76 and 98%, respectively. These results reveal that the amount of PANI in NNMF-PANI1 and NNMF-PANI2 hybrid electrodes is not enough to attain desired conductivity, and also cannot improve the flexible nature of the electrode and thereby reduces the cyclic stability. On the other hand, enhanced coulombic efficiency and cyclic stability of the NNMF-PANI3 electrode is probably due to the uniform distribution of the PANI network between the particles, ensuring the electrolyte is more accessible, thereby decreasing the resistance within the cell and remarkably improving its electrochemical activity. The excellent performance of NNMF-PANI3 is also attributed to the improved Na-ion diffusion and enhanced conductivity, 12 ACS Paragon Plus Environment

Page 13 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


which is in agreement with the results obtained from EIS measurements. In addition, lowing the Rct directly enhances the current flow on the NNMF-PANI3 surface, improving the electrochemical performance of the electrode. EIS measurement of NNMF-PANI composites is also conducted after 60 cycles at 0.75 A g-1 current density, with the curves presented in fig S9. It is evident from fig S9 that the NNMFPANI3 electrode displays the lowest Rct value among all electrodes. This suggests that the optimal concentration of PANI in the composite not only defends the electrode surface from the acidic electrolyte and subsequent metal dissolution, but also stabilizes the solid-electrolyte interface formation, even after the cycling process. These results prove that designing the PANI backbone between the NNMF particles has a noteworthy influence on the electrochemical behavior of the NNMF electrode, particularly in a high cut-off voltage range, and could be used to develop highenergy-density SIBs. Since the NNMF-PANI3 electrode delivered excellent Na-ion storage behaviour, this electrode is chosen to do further physical and electrochemical analysis in comparison to the pristine NNMF electrode. The Raman spectra of NNMF and NNMF-PANI3 hybrid are shown in fig. 5a. Typically, layered compounds exhibit Raman active modes between 400 and 650 cm-1, which are related to the M-O and O-M-O bending modes, respectively, that originate from the vibration of oxygen atoms.41 In the present investigation, the peaks associated with the Raman-active species of Eg and A1g modes are observed at ~ 490 and 587 cm-1, respectively, for both samples. It is clear from fig. 5a that the oscillation strength of the A1g mode has much higher intensity that of the Eg mode. 4243

The FTIR spectrum of NNMF-PANI3 hybrid in fig. 5b displays the characteristic peaks

associated with PANI organic moieties, demonstrating successful oxidation of aniline monomer by APS in the 0.1 M HCl dopant.33 The peaks observed at ~ 1579 and ~ 1489 cm-1 represent the 13 ACS Paragon Plus Environment


Page 14 of 41

stretching vibration of quinoid and benzenoid, respectively, which indicate the presence of its emeraldine salt. 34-35 In the case of NNMF-PANI3, the peak shift observed for quinoid rings toward higher frequencies compared to the parent PANI signify the quinoid rings predominate in the hybrid cathode.32 This suggests that the degree of oxidation of PANI is high due to the interaction with the metal oxide surfaces.34, 38 It is well known that surface interaction between polymer and layered components enhances the conducting properties of pristine materials, thereby improving its electrochemical energy storage behavior.

32-36

The absorption bands located at ~ 1249 and ~

1313 cm-1 could be assigned to the stretching vibration of Ph-N and C-NH+ functionalities of PANI, respectively.

35

The characteristic peak detected at ~ 1133 cm-1 was attributed to the

measurement of the electrons’ delocalization, that is, electronic conductivity. 34-35, 38 Since PANI nanofibers have electrochemical activity at wide potential ranges, the impact of the polymer matrix towards improving the stability is tested at difference operating voltage ranges such as 2-4.2 V and 2-4.5 V. As already seen from fig 3b, the pristine NNMF showed poor Na-ion storage ability at high current densities, and hence the hybrid electrode is also tested at high current densities to check the influence of 0.3 M PANI on the electrochemical performance. The C-D performance of NNMF-PANI3 is studied at 0.2 A g-1 current between 2 and 4.2 V and the corresponding curves are presented in fig. 6a, confirming the better performance of the NNMFPANI3 hybrid electrode compared to pristine NNMF electrodes. A discharge capacity of ~ 125 mAh g-1 could be achieved from hybrid at 0.2 A g-1 current while NNMF electrode delivered only ~ 30 mAh g-1 at the same current density. It is notable that the capacity realized for NNMF-PANI hybrid electrode is much higher than the values reported for O3 type layered sodium-based cathode materials containing iron.

25,29, 44 8, 45-49

Moreover, the NNMF-PANI3 hybrid electrodes exhibit

very stable cyclic stability at 0.2 A g-1 current density, as shown in fig. 6b. The enhanced 14 ACS Paragon Plus Environment

Page 15 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


electrochemical performance of the NNMF-PANI3 electrode is attributed to the improved conductive nature through the formation of porous PANI nanofibers networks between the NNMF particles as illustrated in fig 2e. In addition, uniform distribution of porous PANI conductive networks not only enhances the conductive nature of pristine NNMF particles, but also enables electrolyte adsorption through the open polymer matrix and stabilizes the electrode-electrolyte interface, improving the reversible capacity and stability. 32-33, 36 The C-D curve of the Na+/NNMF-PANI3 cell at 0.1, 0.2 and 0.5 A g-1 currents are given in fig. 6c. As expected, the discharge capacity decreased with increased current rates due to the polarization of the electrodes as well as less participation of active material at high current rates.34, 40

Fig. 6d demonstrates that the NNMF-PANI3 hybrid electrode delivers discharge capacities of ~

137, 125, 100, 90 and 62 mAh g-1 at 0.1, 0.2, 0.5, 1 and 2 A g-1, respectively while the pristine NNMF electrode shows 62, 30, 15 and 11 mAh g-1 at 0.1, 0.2, 0.5, 1 A g-1, respectively. The pristine electrode showed less than 10 mAh g-1 at 2 A g-1 current densities. Further, the NNMFPANI3 electrode retained its capacity of ~ 130 mAh g-1 when the current reverted back to 0.1 A g-1 whereas the pristine NNMF electrode displayed only 54 mAh g-1. The enhanced rate performance of PANI electrode was attributed to its large surface area (37 m2 g-1) and the distribution of a porous conductive network between NNMF particles as observed from BET and SEM images.35 Moreover, the inherent higher electronic conductivity facilitated the electron and Na-ion diffusion rate during the intercalation/de-intercalation process, enhancing reversible capacity and rate capability.34,35,39 Further, the NNMF-PANI3 electrode exhibits stable performance at high current cyclic operation within 2-4.2 V. Fig. S8a presents cyclic behavior of the NNMF-PANI3 cell measured at 2 A g-1 current for 200 cycles. The electrode delivers ~ 62 mAh g-1 capacity during the initial cycle 15 ACS Paragon Plus Environment


Page 16 of 41

and shows stable capacity retention of 97 % after 200 cycles. This outstanding cyclic behavior at high current rate could come from its enhanced morphological and conductive properties.34-35, 50 As observed from the TEM and EDS images in fig. 2f and fig. S7, respectively, the distribution of the highly conductive PANI backbone between the NNMF particles allows for adsorption of more electrolyte

through

the

open

porous

matrix,

intercalation/deintercalation process at high current rates.

which 34-35

improves

the

Na-ion

In the meantime, electrolyte

adsorption within the high surface area NNMF-PANI3 structure also provides a flexible structure against volume expansion/contraction during the cycling progress, thus stabilizing cycling performance even at high current rates.33,35 It is well known that the high polarity of PANI nanofibers makes them compatible with organic electrolytes by adjusting the polarity difference between the active materials and electrolyte.34-36 Moreover, the porous PANI backbone also acts as the reservoir for electrolyte storage. Hence, the electrolyte penetration into the structure is significantly promoted to the electroactive materials compared with conventional conductive additives like amorphous carbon, carbon nanotube etc.34-35 Besides, PANI has slightly higher density compared to carbonaceous materials, which prevents severe detrimental effects of volumetric capacity, delivering high energy storage characteristics.

32, 36.

Fig. S8b presents the

Nyquist plots of the NNMF-PANI3/Na+ cell recorded before and after 50 and 200 cycles at 2 A g-1 current density. The solution resistance of NNMF-PANI3 electrode is slightly increased after 50 and 200 cycles due to unwanted side reactions occurring during the initial cycles.

51

A small

difference of 26.6 Ω in Rct can be observed from table 2 for the cell cycled after 50 and 200 cycles, indicating the NNMF-PANI3 hybrid cathode has excellent Na-ion storage performance between 2 and 4.2 V, which supports the result of the cycling test presented in fig. S8a.

16 ACS Paragon Plus Environment

Page 17 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Since the NNMF prepared with 0.3 M PANI shows excellent capacity retention at lower potentials, the long term cyclability of NNMF-PANI3 hybrid electrode is also investigated at a high operating voltage of 2-4.5 V at high current densities. Fig. 7a illustrates the C-D curves of the NNMF-PANI3 electrode recorded at 0.25, 0.75 and 1.5 A g-1 current densities within 2-4.5 V. Apparently, extended monotonous C-D curves are noted at a high potential window compared to the lower potential range (2-4.2 V) due to the increased participation of Na+ in the electrochemical storage reaction. Moreover, the enhanced electron-conductive nature of the hybrid cathode provided by the conducting polymer PANI matrix directly promotes the redox reaction of transition metals even at high potential range.33,34 Discharge capacities of 162, 115 and 90 mAh g-1 are realized from the NNMF-PANI3 hybrid cathode at current densities of 0.25, 0.75 and 1.5 A g-1, respectively, which is higher than the electrochemical performance of the pristine NNMF electrode as presented in fig 3b and 3c. It is interesting that the NNMF-PANI3 electrode not only delivers higher capacity values at high potential range but also still shows stable cyclic performance as presented in fig. 7b. The NNMF-PANI cell displayed excellent capacity retention of 92 and 94 % after 100 cycles at 0.75 and 2 A g-1 current densities, respectively. In addition, the cell containing NNMF-PANI3 hybrid electrode has discharge capacities of 132 and 79 mAh g-1 at 0.65 and 2 A g-1 current densities (fig. 7c), respectively. An energy density of approximately 567 Wh kg-1 is calculated based on the average cell voltage of 3.5 V at 0.25 A g-1. It is worth mentioning here that the energy density delivered by the NNMF-PANI3 hybrid electrode in the present investigation is comparable with commercial Li-ion batteries electrode materials. For instance, olivine-type LiFePO4 and monoclinic Li2MnO4 materials deliver energy densities of 530 and 450 Wh Kg-1, respectively.1



Page 18 of 41

To the best of our knowledge, the capacity values and stability achieved from the NNMFPANI3 electrode at elevated cycling conditions is the best reported value among O3-layed materials. 24, 44, 46, 52-64 The capacity and stability comparison of various O3-layer materials with NNMF-PANI3 electrode is summarized in table 3, which further demonstrates the enhanced performance of this hybrid electrode. For instance, Yabuuchi et.al obtained a capacity retention of 61 % after only 30 cycles from an O3-Na[Fe0.5Mn0.5]O2 electrode between 1.5-4.3 V at 12 mA g-1. 8, 64

Since the long term cyclability is a key factor to implement any rechargeable energy storage

systems in practical applications, the NNMF-PANI3/Na+ cell is cycled for 750 cycles at 2 A g-1 current density between 2 and 4.5 V with the result presented in fig. 7d. It is clear that the cell is capable of delivering excellent cyclability, maintaining ~ 75 % of its initial value after 750 cycles. This excellent Na-ion storage behaviour even at high cut-off voltage is associated with the conductive PANI nanotubes covered on both the outer and inner surfaces of NNMF particles, which act as a “flexible backbone”, thus preventing electrode structure breakdown and pulverization of the NNMF active species during cycling even at high currents. The energy storage strategy of our investigation can be reiterated by Fig. 8, wherein the PANI conductive matrix ensures the effective ambipolar Na-ion diffusion rate of NNMF regardless of the electrical conductivity. The pristine NNMF electrode suffers huge capacity loss during the Na-ion insertion/extraction process at high current densities, which results from disintegration of the NNMF electrode surface. In addition, the high mechanical stress formed during the cycling process causes the pristine NNMF surface to form cracks, which greatly affects the flow of current on the electrode surface. This uneven current flow results in high resistance, which has great impact on electrode stability. However, the porous PANI network offers more space to accommodate the volume changes, thus mitigating the stress and, preventing structural 18 ACS Paragon Plus Environment

Page 19 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


pulverization during high current cycling. In order to prove this phenomenon, EIS analysis is conducted on the NNMF and NNMF-PANI3 cells after cycling at 0.1 and 0.75 A g-1, respectively for 60 cycles within 2-4.5 V with the corresponding spectra presented in figure S10 in the supporting information. It is clear from figure S10 that the NNMF-PANI3 electrode exhibits lower charge transfer resistance than that of the pristine NNMF electrode even after cycling at high current density. The NNMF-PANI electrode with reduced resistance increases the current flow on the surface and facilitates the electron and Na-ions diffusion rate in the electrode. Moreover, the NNMF particles are hierarchically built up with the PANI nanofiber as shown in figure 8, which avoid the aggregation of NNMF particles and retain small dimensions along with large surface area. Such unique hierarchical structure significantly enhances the Na-ions storage performance by shorting the diffusion paths of Na-ions. The large BET area of NNMF-PANI3 offers more reaction sites for Na-ions intercalation/deintercalation reaction, resulting in high discharge capacity at high currents than the pristine NNMF electrode. These results clearly reveal that adopting PANI to prepare a novel hybrid cathode for RSIB ensures less reactivity towards electrolyte counterparts while increasing the electronic conductivity of the electrode, thus enabling enhanced reversible capacity and cyclability at high current and voltage cycling. Therefore, the NNMF-PANI hybrid could be a promising candidate for next generation electrochemical storage devices.

Conclusion A novel high-performance sodium ion battery is constructed with a new organic–inorganic hybrid of a conducting polymer with a layered Na-intercalating component. The cell fabricated 19 ACS Paragon Plus Environment


Page 20 of 41

with Na(Ni1/3Mn1/3Fe1/3)O2-0.3 M of PANI (NNMF-PANI3) hybrid cathode and Na foil anode exhibits greatly improved Na-ion storage properties compared to that of the pristine NNMF electrode, delivering a maximum discharge capacity ~ 162 mAh g-1 at 0.25 A g-1 rate within a potential window of 2-4.5 V along with excellent cycling behaviour. Further, it also displays excellent stability (~ 75 % capacity retention) even at high current density after 750 cycles with a high cut-off voltage. A maximum energy density value of 567 Wh kg-1 is obtained from the NNMF-PANI based battery, which is comparable with other commercially available lithium-ion battery cathode materials. The hybrid electrode also surpasses the disadvantage of electrolyte depletion during high current cycling due to its structure having a porous polymer network, which also increases Na-ion storage capability at high current rates. Sodium ion batteries containing composites of layered Na-insertion cathode and conducting polymer as energy sources in nonaqueous media represent a new class of improved high-performance electrochemical storage devices. Such devices could be used as potential energy storage systems in low-environmental impact devices such as hybrid and electric vehicles that require high specific energy and improved rate performance, good cycle life, high safety and low cost. Acknowledgements The authors greatly appreciate the financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the University of Waterloo. This work was financially supported by the 111 Project (No. D17007). K.K acknowledges the financial support for this work from Henan Normal University, China.


Page 21 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References (1) Armand, M.; Tarascon, J. M., Building Better Batteries. Nature 2008, 451, 652-657. (2) Palomares, V.; Serras, P.; Villaluenga, I.; Hueso, K. B.; Carretero-Gonzalez, J.; Rojo, T., Na-Ion Batteries, Recent Advances and Present Challenges to Become Low Cost Energy Storage Systems. Energy Environ. Sci. 2012, 5, 5884-5901. (3) Slater, M. D.; Kim, D.; Lee, E.; Johnson, C. S., Sodium-Ion Batteries. Adv. Funct. Mater. 2013, 23, 947-958. (4) Kikkawa, S.; Miyazaki, S.; Koizumi, M., Electrochemical Aspects of the Deintercalation of Layered Amo2 Compounds. J. Power Sources 1985, 14, 231-234. (5) Delmas, C.; Fouassier, C.; Hagenmuller, P., Structural Classification and Properties of the Layered Oxides. Physica B+C 1980, 99, 81-85. (6) Kim, S.-W.; Seo, D.-H.; Ma, X.; Ceder, G.; Kang, K., Electrode Materials for Rechargeable Sodium-Ion Batteries: Potential Alternatives to Current Lithium-Ion Batteries. Adv. Energy Mater. 2012, 2, 710-721. (7) Ding, J.-J.; Zhou, Y.-N.; Sun, Q.; Fu, Z.-W., Cycle Performance Improvement of Nacro2 Cathode by Carbon Coating for Sodium Ion Batteries. Electrochem. Commun. 2012, 22, 85-88. (8) Yabuuchi, N.; Yano, M.; Yoshida, H.; Kuze, S.; Komaba, S., Synthesis and Electrode Performance of O3-Type Nafeo2-Nani1/2mn1/2o2 Solid Solution for Rechargeable Sodium Batteries. J. Electrochem. Soc. 2013, 160, A3131-A3137. (9) Oh, S. M.; Myung, S. T.; Hassoun, J.; Scrosati, B.; Sun, Y. K., Reversible Nafepo4 Electrode for Sodium Secondary Batteries. Electrochem. Commun. 2012, 22, 149-152.



(10)

Page 22 of 41

Barpanda, P.; Liu, G.; Ling, C. D.; Tamaru, M.; Avdeev, M.; Chung, S.-C.;

Yamada, Y.; Yamada, A., Na2fep2o7: A Safe Cathode for Rechargeable Sodium-Ion Batteries. Chem. Mater. 2013, 25, 3480-3487. (11) Li, Y.; Lu, Y.; Zhao, C.; Hu, Y.-S.; Titirici, M.-M.; Li, H.; Huang, X.; Chen, L., Recent Advances of Electrode Materials for Low-Cost Sodium-Ion Batteries Towards Practical Application for Grid Energy Storage. Energy Storage Materials 2017, 7, 130-151. (12) Li, S., et al., Zero-Strain Na2fesio4 as Novel Cathode Material for Sodium-Ion Batteries. ACS App. Mater. Interfaces 2016, 8, 17233-17238. (13) Ortiz-Vitoriano, N.; Drewett, N. E.; Gonzalo, E.; Rojo, T., High Performance ManganeseBased Layered Oxide Cathodes: Overcoming the Challenges of Sodium Ion Batteries. Energy Environ. Sci. 2017, 10, 1051-1074. (14) Billaud, J.; Clément, R. J.; Armstrong, A. R.; Canales-Vázquez, J.; Rozier, P.; Grey, C. P.; Bruce, P. G., Β-Namno2: A High-Performance Cathode for Sodium-Ion Batteries. J. Am. Chem. Soc. 2014, 136, 17243-17248. (15) Komaba, S.; Yabuuchi, N.; Nakayama, T.; Ogata, A.; Ishikawa, T.; Nakai, I., Study on the Reversible Electrode Reaction of Na1–xNi0.5Mn0.5O2 for a Rechargeable Sodium-Ion Battery. Inorg. Chem. 2012, 51, 6211-6220. (16) Yuan, D.; Hu, X.; Qian, J.; Pei, F.; Wu, F.; Mao, R.; Ai, X.; Yang, H.; Cao, Y., P2-Type Na0.67Mn0.65Fe0.2Ni0.15O2 Cathode Material with High-Capacity for Sodium-Ion Battery. Electrochim. Acta 2014, 116, 300-305. (17) Yu, H.; Guo, S.; Zhu, Y.; Ishida, M.; Zhou, H., Novel Titanium-Based O3-Type NaTi0.5Ni0.5O2 as a Cathode Material for Sodium Ion Batteries. Chem. Commun. 2014, 50, 457-459. 22 ACS Paragon Plus Environment

Page 23 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(18) Lu, Z.; Dahn, J. R., In Situ X-Ray Diffraction Study of P2 - Na2 / 3[ Ni1 / 3Mn2 / 3 ] O 2. J. Electrochem. Soc. 2001, 148, A1225-A1229. (19) Ramasamy, H. V.; Kaliyappan, K.; Thangavel, R.; Aravindan, V.; Kang, K.; Kim, D. U.; Park, Y.; Sun, X.; Lee, Y.-S., Cu-Doped P2- P2-Na0.5Ni0.33Mn0.67O2 Encapsulated with Mgo as a Novel High Voltage Cathode with Enhanced Na-Storage Properties. J. Mater. Chem. A 2017. (20) Kaliyappan, K.; Liu, J.; Lushington, A.; Li, R.; Sun, X., Highly Stable Na2/3(Mn0.54Ni0.13Co0.13)O2 Cathode Modified by Atomic Layer Deposition for SodiumIon Batteries. ChemSusChem 2015, 8, 2537-2543. (21) Kaliyappan, K.; Liu, J.; Xiao, B.; Lushington, A.; Li, R.; Sham, T.-K.; Sun, X., Enhanced Performance of P2- Na2/3(Mn0.54Ni0.13Co0.13)O2 Cathode for Sodium-Ion Batteries by Ultrathin Metal Oxide Coatings Via Atomic Layer Deposition. Adv. Funct. Mater. 2017, 27, 1701870-n/a. (22) Wang, L.; Sun, Y.-G.; Hu, L.-L.; Piao, J.-Y.; Guo, J.; Manthiram, A.; Ma, J.; Cao, A.-M., Copper-Substituted Na0.67Ni0.3-xCuxMn0.7O2 Cathode Materials for Sodium-Ion Batteries with Suppressed P2-O2 Phase Transition. J. Mater. Chem. A 2017, 5, 8752-8761. (23) Okada, S.; Takahashi, Y.; Kiyabu, T.; Doi, T.; Yamaki, J.-I.; Nishida, T., Layered Transition Metal Oxides as Cathodes for Sodium Secondary Battery. Meeting Abstracts 2006, MA2006-02, 201. (24) Yabuuchi, N.; Yoshida, H.; Komaba, S., Crystal Structures and Electrode Performance of Alpha- NaFeO2 for Rechargeable Sodium Batteries. Electrochemistry 2012, 80, 716-719. (25) Ado, K.; Tabuchi, M.; Kobayashi, H.; Kageyama, H.; Nakamura, O.; Inaba, Y.; Kanno, R.; Takagi, M.; Takeda, Y., Preparation of LiFeO2 with Alpha‐ Na FeO2‐Type Structure 23 ACS Paragon Plus Environment


Page 24 of 41

Using a Mixed‐Alkaline Hydrothermal Method. J. Electrochem. Soc. 1997, 144, L177L180. (26) Kim, S.; Ma, X.; Ong, S. P.; Ceder, G., A Comparison of Destabilization Mechanisms of the Layered NaxMO2 and LixMO2 Compounds Upon Alkali De-Intercalation. Phys. Chem. Chem. Phys. 2012, 14, 15571-15578. (27) Nayak, P. K.; Yang, L.; Brehm, W.; Adelhelm, P., From Lithium-Ion to Sodium-Ion Batteries: Advantages, Challenges, and Surprises. Angew. Chem. Int. Ed. 2018, 57, 102120. (28) Yoshida, H.; Yabuuchi, N.; Komaba, S., NaFe0.5Co0.5O2 as High Energy and Power Positive Electrode for Na-Ion Batteries. Electrochem. Commun. 2013, 34, 60-63. (29) Kim, D.; Lee, E.; Slater, M.; Lu, W.; Rood, S.; Johnson, C. S., Layered Na[Ni1/3Fe1/3Mn1/3]O2 Cathodes for Na-Ion Battery Application. Electrochem Commun 2012, 18, 66-69. (30) Sathiya, M.; Hemalatha, K.; Ramesha, K.; Tarascon, J. M.; Prakash, A. S., Synthesis, Structure, and Electrochemical Properties of the Layered Sodium Insertion Cathode Material: Na[Ni1/3Fe1/3Mn1/3]O2 Chem. Mater. 2012, 24, 1846-1853. (31) Novák, P.; Müller, K.; Santhanam, K. S. V.; Haas, O., Electrochemically Active Polymers for Rechargeable Batteries. Chem. Rev. 1997, 97, 207-282. (32) Zhang, P.; Zhang, L.; Ren, X.; Yuan, Q.; Liu, J.; Zhang, Q., Preparation and Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2–PPy Composites Cathode Materials for Lithium-Ion Battery. Synth. Met. 2011, 161, 1092-1097. (33) Perez-Cappe, E.; Mosqueda, Y.; Martinez, R.; Milian, C. R.; Sanchez, O.; Varela, J. A.; Hortencia, A.; Souza, E.; Aranda, P.; Ruiz-Hitzky, E., Preparation and Properties as 24 ACS Paragon Plus Environment

Page 25 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Positive Electrodes of PANI-LiNi0.8Co0.2O2 nanocomposites. J. Mater. Chem. 2008, 18, 3965-3971. (34) Karthikeyan, K.; Amaresh, S.; Aravindan, V.; Kim, W. S.; Nam, K. W.; Yang, X. Q.; Lee, Y. S., Li(Mn1/3Ni1/3Fe1/3)O2–Polyaniline Hybrids as Cathode Active Material with UltraFast Charge–Discharge Capability for Lithium Batteries. J. Power Sources 2013, 232, 240245. (35) Karthikeyan, K.; Amaresh, S.; Aravindan, V.; Kim, H.; Kang, K. S.; Lee, Y. S., Unveiling Organic-Inorganic Hybrids as a Cathode Material for High Performance Lithium-Ion Capacitors. J. Mater. Chem. A 2013, 1, 707-714. (36) Huang, Y.-H.; Goodenough, J. B., High-Rate Lifepo4 Lithium Rechargeable Battery Promoted by Electrochemically Active Polymers. Chem. Mater. 2008, 20, 7237-7241. (37) Zhou, Q.; Liu, L.; Huang, Z.; Yi, L.; Wang, X.; Cao, G., Co3S4@Polyaniline Nanotubes as High-Performance Anode Materials for Sodium Ion Batteries. J. Mater. Chem. A 2016, 4, 5505-5516. (38) Huang, W.-S.; Humphrey, B. D.; MacDiarmid, A. G., Polyaniline, a Novel Conducting Polymer. Morphology and Chemistry of Its Oxidation and Reduction in Aqueous Electrolytes. J. Chem. Soc., Faraday Trans. 1 1986, 82, 2385-2400. (39) Kim, D.; Kang, S.-H.; Slater, M.; Rood, S.; Vaughey, J. T.; Karan, N.; Balasubramanian, M.; Johnson, C. S., Enabling Sodium Batteries Using Lithium-Substituted Sodium Layered Transition Metal Oxide Cathodes. Adv. Energy Mater. 2011, 1, 333-336. (40) Karthikeyan, K.; Amaresh, S.; Lee, G. W.; Aravindan, V.; Kim, H.; Kang, K. S.; Kim, W. S.; Lee, Y. S., Electrochemical Performance of Cobalt Free, Li1.2(Mn0.32Ni0.32Fe0.16)O2 cathodes for lithium batteries. Electrochim. Acta 2012, 68, 246-253. 25 ACS Paragon Plus Environment


Page 26 of 41

(41) Karthikeyan, K.; Amaresh, S.; Kim, S. H.; Aravindan, V.; Lee, Y. S., Influence of Synthesis Technique on the Structural and Electrochemical Properties of “Cobalt-Free”, Layered Type Li1+x(Mn0.4Ni0.4Fe0.2)1−xO2 (0˃x˃0.4) cathode material for lithium secondary battery. Electrochim. Acta 2013, 108, 749-756. (42) Karthikeyan, K.; Amaresh, S.; Aravindan, V.; Kim, W. S.; Nam, K. W.; Yang, X. Q.; Lee, Y. S., Li(Mn1/3Ni1/3Fe1/3)O2–Polyaniline hybrids as cathode active material with ultra-fast charge–discharge capability for lithium batteries. J. Power Sources 2013, 232, 240-245. (43) Julien, C., Local Cationic Environment in Lithium Nickel–Cobalt Oxides Used as Cathode Materials for Lithium Batteries. Solid State Ion. 2000, 136–137, 887-896. (44) Yabuuchi, N.; Kajiyama, M.; Iwatate, J.; Nishikawa, H.; Hitomi, S.; Okuyama, R.; Usui, R.; Yamada, Y.; Komaba, S., P2-type Nax[Fe1/2Mn1/2]O2 made from earth-abundant elements for rechargeable Na batteries. Nat. mater. 2012, 11, 512-517. (45) Yuan, D.; Liang, X.; Wu, L.; Cao, Y.; Ai, X.; Feng, J.; Yang, H., A Honeycomb-Layered Na3Ni2SbO6: A High-Rate and Cycle-Stable Cathode for Sodium-Ion Batteries. Adv. Mater. 2014, 26, 6301-6306. (46) Vassilaras, P.; Kwon, D.-H.; Dacek, S. T.; Shi, T.; Seo, D.-H.; Ceder, G.; Kim, J. C., Electrochemical Properties and Structural Evolution of O3-Type Layered Sodium Mixed Transition Metal Oxides with Trivalent Nickel. J. Mater. Chem. A 2017, 5, 4596-4606. (47) Kubota, K.; Yabuuchi, N.; Yoshida, H.; Dahbi, M.; Komaba, S., Layered Oxides as Positive Electrode Materials for Na-Ion Batteries. MRS Bull. 2014, 39, 416-422. (48) Hwang, J.-Y.; Myung, S.-T.; Choi, J. U.; Yoon, C. S.; Yashiro, H.; Sun, Y.-K., Resolving the Degradation Pathways of the O3-Type Layered Oxide Cathode Surface through the


Page 27 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Nano-Scale Aluminum Oxide Coating for High-Energy Density Sodium-Ion Batteries. J. Mater. Chem. A 2017, 5, 23671-23680. (49) Guo, S.; Yu, H.; Liu, P.; Ren, Y.; Zhang, T.; Chen, M.; Ishida, M.; Zhou, H., HighPerformance Symmetric Sodium-Ion Batteries Using a New, Bipolar O3-Type Material, Na0.8ni0.4ti0.6o2. Energy Environ. Sci. 2015, 8, 1237-1244. (50) Karthikeyan, K.; Lee, Y. S., Microwave Synthesis of High Rate Nanostructured Limnbo3 with Excellent Cyclic Behavior for Lithium Ion Batteries. RSC Adv. 2014, 4, 31851-31854. (51) Thangavel, R.; Kaliyappan, K.; Kang, K.; Sun, X.; Lee, Y.-S., Going Beyond Lithium Hybrid Capacitors: Proposing a New High-Performing Sodium Hybrid Capacitor System for Next-Generation Hybrid Vehicles Made with Bio-Inspired Activated Carbon. Adv. Energy Mater. 2016, 6, 1502199-n/a. (52) Zheng, L.; Obrovac, M. N., Investigation of O3-Type Na0.9Ni0.45MnxTi0.55-xO2 (0 ≤ x ≤ 0.55) as positive electrode materials for sodium-ion batteries. Electrochimica Acta 2017, 233, 284-291. (53) Yoshida, H.; Yabuuchi, N.; Komaba, S., NaFe0.5Co0.5O2 as high energy and power positive electrode for Na-ion batteries. Electrochem. Commun. 2013, 34, 60-63. (54) Wang, X.; Liu, G.; Iwao, T.; Okubo, M.; Yamada, A., Role of Ligand-to-Metal Charge Transfer in O3-Type NaFeO2–NaNiO2 Solid Solution for Enhanced Electrochemical Properties. J. Phy. Chem. C 2014, 118, 2970-2976. (55) Wang, P.-F.; Yao, H.-R.; Liu, X.-Y.; Zhang, J.-N.; Gu, L.; Yu, X.-Q.; Yin, Y.-X.; Guo, Y.-G., Ti-Substituted NaNi0.5Mn0.5-xTixO2 Cathodes with Reversible O3−P3 Phase Transition for High-Performance Sodium-Ion Batteries. Adv. Mater. 2017, 29, 1700210n/a. 27 ACS Paragon Plus Environment


Page 28 of 41

(56) Vassilaras, P.; Dacek, S. T.; Kim, H.; Fister, T. T.; Kim, S.; Ceder, G.; Kim, J. C., Communication—O3-Type Layered Oxide with a Quaternary Transition Metal Composition for Na-Ion Battery Cathodes: NaTi0.25Fe0.25Co0.25Ni0.25O2. J. Electrochem. Soc. 2017, 164 (14), A3484-A3486. (57) Takeda, Y.; Nakahara, K.; Nishijima, M.; Imanishi, N.; Yamamoto, O.; Takano, M.; Kanno, R., Sodium Deintercalation from Sodium Iron Oxide. Mater. Res. Bull. 1994, 29, 659-666. (58) Su, N.; Lyu, Y.; Guo, B., Electrochemical and in-Situ X-Ray Diffraction Studies of Na1.2Ni0.2Mn0.2Ru0.4O2 as a cathode material for sodium-ion batteries. Electrochem. Commun. 2018, 87, 71-75. (59) Sato, K.; Nakayama, M.; Glushenkov, A. M.; Mukai, T.; Hashimoto, Y.; Yamanaka, K.; Yoshimura, M.; Ohta, T.; Yabuuchi, N., Na-Excess Cation-Disordered Rocksalt Oxide: Na1.3nb0.3mn0.4o2. Chem. Mater. 2017, 29, 5043-5047. (60) Oh, S.-M.; Myung, S.-T.; Yoon, C. S.; Lu, J.; Hassoun, J.; Scrosati, B.; Amine, K.; Sun, Y.-K., Advanced Na[Ni0.25Fe0.5Mn0.25]O2/C–Fe3O4 Sodium-Ion Batteries Using EMS Electrolyte for Energy Storage. Nano Lett. 2014, 14, 1620-1626. (61) Oh, S.-M.; Myung, S.-T.; Hwang, J.-Y.; Scrosati, B.; Amine, K.; Sun, Y.-K., High Capacity O3-Type Na[Li0.05(Ni0.25Fe0.25Mn0.5)0.95]O2 Cathode for Sodium Ion Batteries. Chem. Mater. 2014, 26, 6165-6171. (62) Nanba, Y., et al., Redox Potential Paradox in NaxMO2 for Sodium-Ion Battery Cathodes. Chem. Mater. 2016, 28, 1058-1065. (63) Mortemard de Boisse, B.; Carlier, D.; Guignard, M.; Delmas, C., Structural and Electrochemical Characterizations of P2 and New O3- O3-NaxMn1-yFeyO2 Phases Prepared 28 ACS Paragon Plus Environment

Page 29 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


by Auto-Combustion Synthesis for Na-Ion Batteries. J. Electrochem. Soc. 2013, 160, A569-A574. (64) Hwang, J.-Y.; Myung, S.-T.; Sun, Y.-K., Sodium-Ion Batteries: Present and Future. Chem. Soc. Rev. 2017, 46, 3529-3614.



Page 30 of 41

Fig. 1 The Rietveld refinement analysis of (a) NNMF and (b) NNMF-PANI1, (c) NNMF-PANI2 and (d) NNMF-PANI3 powders. The refined crystal structure of NNMF is presented as insert in fig. 1a.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

(c)

25 nm

dV/dW (cm-3 g-1 nm-1

Page 31 of 41

(b)

NNMF

PANI

NNMF

PANI

200 nm

50 nm

(f)

(e)

(d)

0

25

50

75

200 nm 100

125

Pore Diameter (nm)

NNMF NNMF NNMF

NNMF PANI PANI

PANI PANI PANI

NNMF

PANI

NNMF particles

PANI

200 nm

e-1/Na+

PANI

Porous PANI matrix

200 nm

Fig. 2 TEM image of (a) NNMF, (b) PANI, (c) NNMF-PANI1, (d) NNMF-PANI2, (e) NNMFPANI3 and (f) schematic illustration of Na-ion diffusion pathway NNMF-PANI hybrid electrode.


e-1/Na+


Voltage (V)

4.2

(a)

3.6 3.0 2.4 0

-1 -1 Capacity (mAh g ) Voltage (V) Capacity (mAh g )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 41

200

40

(b)

150

80

120 -1

160

Capacity (mAh g ) -1

g-1 -1 0.1 A mAg

A g-1 0. 02 mAg

-1

g-1 0.2 A mAg

100 50 0 4.2

10

20

30

40

Cycle number

50

(c)

3.6 3.0 2.4

20 100 80 60 40 20 0

40

60

-1

Capacity (mAh g )

80

100

(d)

0

6

12

18

Cycle number

24

30

Fig. 3 C-DC profile of NNMF electrode at 0.02 A g-1 between 2 and 4.2 V, (b) cyclic stability of NNMF electrode at various current densities. (c) and (d) C-D and cyclic stability of PANI electrode, respectively, recorded at 0.2 A g-1 within 2-4.2 V potential range . 32 ACS Paragon Plus Environment

Page 33 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 4 (a) EIS spectra of pristine and NNMF-PANI composites measured at open circuit voltage, (b) C-D and cycle life (insert in fig. b) of pristine NNMF electrode cycled at 0.1 A g-1 within 24.5 V, (c) C-D and (d) cyclic performance of NNMF-PANI hybrid electrodes at 0.75 A g-1 current density between 2 and 4.5 V



300

400

500

600

700

800

Wave number (cm-1)

900 1000

PANI NNMF-PANI3

750

1000

1250

1579

1489

1249 1133

1313

(b)

Transmitance (%)

NNMF PANI-NNMF3

(a) Intensity (a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 41

1500

1750

Wave number (cm-1)

Fig 5 (a) Raman Spectrum of pristine and hybrid composite materials and (b) FT-IR spectrum of PANI and NNMF-PANI3 composites


2000

4.2

(a)

3.6

NNMF

3.0

NNMF-PANI3

2.4

-1

0

25

50

75

100

125

-1

Capacity (mAh g )

(b)

150

NNMF

150

NNMF-PANI3

100 50 0

0

10

20

30

40

50

Cycle number 4.2

(c)

3.6

-1

0.1 A g

-1

3.0

0.2 A g

2.4

0.5 A g

-1

50

-1

Capacity (mAh g )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Voltage (V) Capacity (mAh g ) Voltage (V)

Page 35 of 41

100

-1

150

200

Capacity (mAh g ) 200 150 100 50 0

(d)

0

-1

0.1 A g

5

-1

0.2 A g

10

NNMF -1

0.5 A g

NNMF-PANI3 -1

-1

1Ag

15

0.1 A g -1

2Ag

20

25

30

Cycle number

Fig. 6 (a) C-D curves and (b) cyclic performance of NNMF and NNMF-PANI3 hybrid cathode recorded at 0.2 A g-1 within 2-4.2 V range, (c) C-D curves of NNMF-PANI3 cathode at various current densities and (d) rate performance of pristine and hybrid cathode at different current rates.


4.5 4.0 3.5 3.0 2.5 2.0

120 90 60 30 0 200

(a)

60

100 75 50 25 0

120

180

0.75 A g

0

20 0.5 A g

0.75 A g

40

-1 0.65 A g

-1

1Ag

60

3

-1

80

100

-1 0.75 A g-1

1 A g-1

2 A g-1

(c) 0

-1

240

Capacity (mAh g-1)

(b)

100 50

-1 0.5 A g -1 1Ag

0

150

Page 36 of 41

6

9

12

15

Efficiency (%)

Capacity (mAh g-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Voltage (V)


100 80

(d) 0

200

400

600

800

60 1000

Cycle Number

Fig. 7 C-D profile of NNMF-PANI3 hybrid cathode at different current densities between 2 and 4.5 V, (b) cyclic and (c) rate performance of NNMF-PANI3 electrode at different current density. (d) long term cyclicality of NNMF-PANI3 hybrid cathode at 2 A g-1 for 750 cycles within 2-4.5 V


Page 37 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 8 Illustration of Na-ion storage and ionic movement within the hybrid cathode structure.



Page 38 of 41

Table 1: Lattice content of NNMF and NNMF-PANI materials Material

ah (Å)

ch (Å)

c/a

I(003)/I(104) ratios

Rp (%)

Rwp (%)

NNMF

2.875

14.235

4.95

0.942

5.038

7.145

NNMF-PANI1

2.873

14.232

4.95

0.939

5.054

6.925

NNMF-PANI2

2.876

14.237

4.94

0.949

5.415

6.512

NNMF-PANI3

2.867

14.229

4.94

0.944

5.221

6.478


Page 39 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2: The electrochemical impedance parameters of pristine and NNMF-PANI3 electrodes before and after cycled between 2 and 4.2 V Rs (Ω) Sample

Rct (Ω)

1st cycle

50 th cycle

200 th cycle

1st cycle

50 th cycle

200 th cycle

NNMF

25.02

-

-

204.6

-

-

NNMF-PANI3

26.76

38.63

41.24

118.1

443.58

470.24


The Journal of Physical Chemistry 1 2 3 4 5 Table 3: Comparison 6 7 Materials 8 9 10 α-NaFeO2 11 12 O3-Na[Ni1/3Fe1/3Mn1/3]O2 13 14 O3-Na[Fe0.5Mn0.5]O2 15 16 O3-NaNi0.5Fe0.5O2 17 18 19 O3-Na0.9Ni0.45Mn0.33Ti0.25O2 20 O3-O3-NaFe0.5Co0.5O2 21 22 O3-NaFe0.3Ni0.7O2 23 24 O3-NaNi0.5Mn0.2Ti0.3O2 25 26 O3-NaTi0.25Fe0.25Co0.25Ni0.25O2 27 28 O3-Na0.5FeO2 29 30 O3-Na Ni Mn Ru O 1.2 0.2 0.2 0.4 2 31 32 O3-Na1.3Nb0.3Mn0.4O2 33 34 O3-Na[Ni0.25Fe0.5Mn0.25]O2 35 36 O3-NaLi0.05Ni0.23Fe0.24Mn0.475O2 37 O3-NaFe0.5Ni0.5O2 38 39 O3-NaFe0.5Co0.5O2 40 41 O3-NaFe0.67Mn0.33O2 42 43 O3-NNMF 44 45 O3-NNMF-PANI3 46 47 O3-NNMF-PANI3 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 41

of cyclic stability of NNMF-PANI with various O3 layered materials Voltage range (V)

Current density

Capacity (mAh g-1)

Capacity retention (%)

Reference

2.5-3.5

12 mA g-1

100

60 % after 30 cycles

8

2-4

13 mA g-1

122


27

1.5-4.3

12 mA g-1

126


42

2-4.2

20 mA g-1

150


44

1.5 - 4.2

12 mA g-1

148

80 % after 5 cycles

50

2.5-4

12 mA g-1

140


51

2.5-3.8

30 mA g-1

135


52

2-4.2

240 mA g-1

120


53

2-4.2

12 mA g-1

145


54

1-4

0.25 mA cm-2

80

Not given

55

1.5–3.8

52 mA g-1

119


56

1-4

13 mA g-1

200


57

0.5-3.6

13 mA g-1

130


58

1.7-4.4

65 mA g-1

135


59

2-3.8

30 mA g-1

128


60

2-3.8

30 mA g-1

138


60

1.5-3.8

13 mA g-1

136


61

2-4.2

20 mA g-1

129


Present work

2-4.5

750 mA g-1

115


Present work

2-4.5

2, 000 mA g-1

79

~ 75 % after 750 cycles

Present work


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC Graphic

e-1/Na+ NNMF particles

e-1/Na+

Porous PANI matrix

100

Na(Ni1/3Fe1/3Mn1/3)O2 Na1.2(Ni0.2Ru0.4Mn0.2)O2

90

Enhanced Performance Hybrid Cathode

Stability (%)

Page 41 of 41

Na(Co0.5Fe0.5)O2 Na(Ni0.5Ti0.2Mn0.3)O2 Na0.9(Ni0.45Ti0.25Mn0.33)O2 NaLi0.05(Ni0.25Fe0.24Mn0.475)O2 Na(Ni0.25Fe0.5Mn0.25)O2 NNMF-PANI3 Na (Ni Fe )O

80 70

0.9

0.7

0.3

2

Na(Mn0.5Fe0.5)O2

60

Na1.3(Nb0.3Mn0.5)O2

50

NaFeO2

0

100

200

300

400

500

600

700

800

Cycle life


Rational Design of Environmental Benign Organic-Inorganic Hybrid as

Recommend Documents